Wood joint connector plates are used for connecting wood members to form trusses, joists, beams and the like. These plates are made of thin, rigid sheet steel, such as galvanized steel, and are provided with struck-out teeth that embed into the adjacent wood members. Examples of connector plates are disclosed in U.S. Pat. Nos. 3,633,454, issued Jan. 11, 1972 to Schmitt et al., 3,951,033, issued Apr. 20, 1976 to Moehlenpah, 4,318,652, issued Mar. 9, 1982 to Gore, 4,343,580, issued Aug. 9, 1982 to Moyer et al. and related U.S. Pat. No. 4,639,176, issued Jan. 27, 1987 to Smith et al.
The connector plates are typically applied by first arranging the wood members, which are to be connected, in position to form a joint. A plate is placed over the joint location and then is pressed against the wood, using a suitable compression clamp or by hammering, so that its teeth embed into the wood. Ordinarily, a pair of plates are used, one on each side of the wood member joint.
The wood members which, for example, may be in the form of 2.times.4 strips, 2.times.6 strips, etc. may be positioned so as to form different shapes and styles of joints. For example, two wood strips may be arranged side-by-side and joined together to form a double-thick wood strip beam. As another example, abutting ends of aligned wood strips may be joined together to form a double length strip. As an example of a truss or a joist construction, the end of one wood strip may be cut at an angle which is abutted against a second wood strip. These strips may be joined together to form a V-shaped joint used in a truss or a joist.
Since wood and wood fibers are relatively flexible, after a period of time, there is a tendency for the teeth of a connector plate to loosen relative to the wood piece in which they are embedded. This loosening effect may be due to weather conditions, temperature changes, moisture, or load induced movement of the wood members, etc. For example, varying loads upon floor joists or roof trusses cause some movement of the wood elements and tends to loosen the connector plate teeth at the joints.
Further, connector plates are designed to support predetermined shear loads. Consequently, the number of plates, the size and thicknesses of plates, and the number of their teeth are ordinarily increased to handle anticipated high shear loads.
In the past, attempts have been made to design connector plate teeth which resist loosening from the wood into which they are embedded, and to increase their shear load strength. Thus, there has been a need for better connector plates whose teeth more tightly grip and intertwine with the wood fibers of the wood members in which they are embedded and which have a greater load carrying capacity. This invention relates to an improvement in connector plates for this purpose.